The Nano X4 training shoes are one of the lightest, most breathable versions of the Nano. These Reebok training shoes are designed with enhanced stability and support, without excessive design features that add weight. The new Flexweave (R) woven textile upper is ultra-lightweight, and a new midfoot ventilation panel allows better air circulation. The innovative Lift and Run Chassis system ensures optimum stability, while Floatride Energy Foam cushions every stride.